1. Field of the Invention
The invention relates to an intra-aortic balloon (IAB) catheter. More particularly, the invention relates to an IAB catheter capable of being removed through its insertion sheath.
2. Description of the Prior Art
Intra-aortic balloon (IAB) catheters are used in patients with left heart failure to augment the pumping action of the heart. The catheters, approximately 1 meter long, have an inflatable and deflatable balloon at the distal end. The catheter is typically inserted into the femoral artery and moved up the descending thoracic aorta until the distal tip of the balloon is positioned just below or distal to the left subclavian artery. The proximal end of the catheter remains outside of the patient""s body. A passageway for inflating and deflating the balloon extends through the catheter and is connected at its proximal end to an external pump. The patient""s central aortic pressure is used to time the balloon and the patient""s ECG may be used to trigger balloon inflation in synchronous counterpulsation to the patient""s heart beat.
Intra-aortic balloon therapy increases coronary artery perfusion, decreases the workload of the left ventricle, and allows healing of the injured myocardium. Ideally, the balloon should be inflating immediately after the aortic valve closes and deflating just prior to the onset of systole. When properly coordinated, the inflation of the balloon raises the patient""s diastolic pressure, increasing the oxygen supply to the myocardium; and balloon deflation just prior to the onset of systole lowers the patient""s diastolic pressure, reducing myocardial oxygen demand.
Intra-aortic balloon catheters may also have a central passageway or lumen which can be used to measure aortic pressure. In this dual lumen construction, the central lumen may also be used to accommodate a guide wire to facilitate placement of the catheter and to infuse fluids, or to do blood sampling.
Typical dual lumen intra-aortic balloon catheters have an outer, flexible, plastic tube, which serves as the inflating and deflating gas passageway, and a central tube therethrough formed of plastic tubing, stainless steel tubing, or wire coil embedded in plastic tubing. A polyurethane compound is used to form the balloon.
A great deal of effort has been exerted in an effort to reduce the outer diameter of the IAB catheter. A reduction in size is desired in order to minimize the size of the arterial opening, to facilitate insertion of the catheter into the aorta, maximizing blood flow past the inserted catheter, and also to allow for the use of a smaller insertion sheath to further maximize distal flow. Progress has certainly been made: IAB catheters currently on the market have outer diameters of as low as 8.0 Fr compared to over 10.0 Fr only a few years ago.
Despite the drastic reduction of catheter size, patients undergoing an IAB procedure still suffer a relatively large arterial opening compared to the outer diameter of the IAB catheter. IAB catheters are inserted into the body with the balloon membrane tightly wrapped about the inner tube. The balloon membrane is generally tightly wrapped such that the outer diameter of the wrapped balloon is equal to or slightly larger than the outer diameter of the catheter. Upon removal of the IAB catheter from the patient, however, the balloon membrane is no longer wrapped about the inner tube and cannot be easily removed through the insertion sheath. Thus, removal of the IAB catheter requires removal of the insertion sheath and withdrawal of the IAB catheter directly through the arterial opening. This process may damage the blood vessel or enlarge the arterial opening created during insertion of the IAB catheter. Accordingly, a need exists for a IAB catheter capable of being removed through the same sheath used for its insertion.
One method which is generally used to minimize the size of the balloon membrane prior to removal of the IAB catheter from the patient involves creating a vacuum in the balloon membrane. The reduction in size generated by this method, however, is insufficient to allow withdrawal of the IAB catheter through the insertion sheath.
A similar removal problem has been noted in the angioplasty balloon catheter context and a number of solutions have been posed.
U.S. Pat. Nos. 5,087,246, 5,195,970, 5,226,887, 5,456,666, and 5,458,572, disclose balloon catheters having balloons which collapse into a more readily removable low profile configuration.
U.S. Pat. No. 5,681,522, discloses a balloon catheter having a balloon which was annealed to introduce a memory component into the plastic of the balloon that causes it to assume a lower profile upon deflation then otherwise obtained.
U.S. Pat. No. 4,608,984 discloses a balloon catheter having a second balloon disposed about a first balloon. Said second balloon is used to compress and evacuate the chamber of the first balloon in order to facilitate removal of the catheter.
A catheter capable of being removed through the same insertion sheath as used for its insertion is valuable for another reason besides for its minimization of the arterial size opening. Namely, such a catheter allows a surgeon to leave the insertion sheath in place after removal of the IAB catheter. Upon completion of therapy a surgeon may want to leave the insertion sheath in place until he or she is confident that further therapy will not be required. Similarly, a surgeon, during therapy, may want to switch to a different size IAB catheter or completely replace an inoperative IAB catheter. The present invention obviates the need to reinsert the insertion sheath in these situations.
A need also exists for an IAB catheter which minimizes the amount of arterial insertion site bleeding. The outer diameter of the wrapped balloon membrane of catheters currently on the market is generally larger than the outer diameter of the catheter outer tube. Upon insertion of the IAB catheter the wrapped balloon membrane over dilates the tissue tract and the arterial insertion site beyond the outer diameter of the catheter outer tube. This over dilation creates an annular gap, between the outer surface of the insertion sheath and the tissue tract or between the outer surface of the inserted catheter outer tube and the tissue tract in a sheathless procedure, through which blood escapes during the procedure. Accordingly, a need exists for an IAB catheter whose wrapped balloon membrane does not over dilate the tissue tract and the arterial opening upon insertion beyond the outer diameter of the catheter outer tube.
A need further exists for a sheathlessly inserted IAB catheter capable of being removed without drastically increasing the arterial opening. Similar to percutaneous procedures incorporating sheaths, sheathless procedures also involve the removal of an unfurled balloon membrane.
Accordingly, it is an object of the invention to produce an intra-aortic balloon catheter capable of being withdrawn through its insertion sheath upon completion of therapy.
It is another object of the invention to produce an insertion sheath capable of having an unfurled intra-aortic balloon membrane withdrawn through it.
It is a further object of the invention to produce a sheathlessly insertable intra-aortic balloon catheter capable of being withdrawn from the artery without significantly increasing the size of the arterial opening.
It is still a further object of the invention to produce an intra-aortic balloon catheter which minimizes arterial bleeding at the insertion site.
It is still yet a further object of the invention to produce an intra-aortic balloon catheter which permits a surgeon the flexibility to leave the insertion sheath in the artery despite removal of the intra-aortic balloon catheter, thus, obviating the need to reinsert the insertion sheath upon reinitiation of therapy or upon replacement of the intra-aortic balloon catheter.
The invention is an improved intra-aortic balloon catheter system comprising an insertion sheath, having an expandable distal end, and a tapered balloon membrane capable of being removed through said insertion sheath upon completion of therapy. The outer diameter of the balloon membrane in a wrapped state is smaller than the outer diameter of the outer tube.
To the accomplishment of the above and related objects the invention may be embodied in the form illustrated in the accompanying drawings. Attention is called to the fact, however, that the drawings are illustrative only. Variations are contemplated as being part of the invention, limited only by the scope of the claims.